Mobile devices such as cellular telephones, smart phones, and other handheld or portable electronic devices such as personal digital assistants (“PDAs”), headsets, and MP3 players have become popular and ubiquitous. Such devices are used for business and entertainment, and can also assist users with everyday tasks. As more and more features are incorporated into mobile devices, there is an increasing desire to equip these mobile devices with input/output mechanisms that accommodate numerous user commands and/or react to numerous user behaviors.
It is of particular interest that mobile devices be capable of detecting the presence and position of physical objects located outside of a mobile device. Within this field of interest, it is of particular interest that such devices be able to detect the presence and determine the location of nearby personnel or their heads, hands, etc. Such personnel may be users of the device or may simply be individuals located nearby the device. One result of such detection and determination capability is to allow the mobile device to adjust its behavior as appropriate given the presence (or absence) and location of the human beings and/or other physical objects.
While remote sensing devices such as infrared (or, more accurately, near-infrared) transceivers have been employed in the past in some mobile devices to allow for the detection of the presence and/or location of human beings and/or physical objects, such sensing devices have been limited in various respects. In particular, some such near-infrared transceivers in some such mobile devices are only able to detect actual movement of the person or object, but are not able to detect the continuous presence of the person or object. Moreover, some such transceivers in some such mobile devices are undesirably complicated, requiring large numbers of components in order to operate, or requiring optical elements that attenuate the received infrared signals. The additional elements and complication of such systems render such devices unduly expensive and inefficient.